Radio circuits employing alternating current radio tubes



Aug. 18, 1931. F. s. MGCULLOUGH RADIO CIRCUITS EMPLOYING ALTERNATING CURRENT RADIO TUBES Filed May 4, 1925 ATTORNEY Patented 'Aug. 18, 1931 IBH'H'JBICI srflccULLoUGn, F WILKINS BUBG, PENNSYLVANIA."

mic cincurrs surname ALTERNATING cums RADIO 'ruims Application med m f4, 925. semi no. 27,079..

This invention relates to a method of and acircuit forusing radio tubes of the type having a cathode and a heater for the a cathode; The invention pertains especially I to theuse of tubes constructed inaccordance with my co-pending application for Patent Serial No. 12,477, led March 2, 1925.

While atube as constructed in accordance with; my said invention effectively eliminates inductance efiects of alternating pulsating.

currents in the tube itself, it is desirable, when using the tube in a set, 'to'eliminate any reaction or capacity effects between'the alternating or. pulsating heater circuit and 15 the tube circuit'per se.

v The presentinvention has for its object to provide a simple and "convenient way of avoiding such reactions or efltects;

Furthermore, in a tube'of this type, there is only one cathode connection in the base,

whereas, the usual tube having the direct heated cathode or filament has two cathode connections in: its base, which cathode connections, make circuit with the filament heating or A battery, and whereas this A battery is not required with my tube, it will be seen that there is an open circuit across the usual A" battery terminals of the receiving circuit.

According to a further. object of the present invention, I propose to utilize present circuits in standard sets, or circuits'in appa-' ratus built specially for use with my tubes grounding the cathodeofthe tube 0 thef common ground of the circuit through a small battery connected across' what correspondsto the A battery circuit of present sets, so that the cathode of each tube in the circuit will'havea potential on the gri In other words, an object of the present invention is to so utilize stituted'across the terminals of what has heretofore been the A battery'circuit, to bias the grid and avoid opening the circuit of" each tube for a C battery connection.

The nature of the invention may be more readily understood by reference totheaccompanying drawings, in which:

positive A dpotential opposite the I;

Fig. 1 is a simple circuit diagram illustrating the principle of the invention; Fi' 2 represents a vertical section through a tu e of the type shown in my said copending application; and

Fig. 3 is an end view of the base of the tube. I

In the drawings, Fig. 2 may be first re-' ferred to as illustrating'the type of tube in connection with which the resent invention is preferably to be practice In this figure, 5 designates the envelope of the tube, 6 the base, 7 the stem of the tube, and 8 is the plate or anode supported, by wire 9 passing through the stem and attaching to pin 10 on the base. The grid isdesignated 11 and is supported on wire 12 passing through the stem and connecting with pin 13 on t e ase.

Thecathode of the tube is a shell or tubular member 14 on a porcelain or othersuitable rod 15. In the upper end of the rod,

y-above the grid, is'a resistance wire 16.- Ourrent is supplied to the resistance element 16 through wires 17 entering through an upper stem 18. These'wires may connect with pins 19 in an upper cap 20. When the resistance wire is energized,.the heat-is carried along the porcelain stem to 'the metallic member 14, heating it toa point where it will sustain electron emission. Connection is made to the cathode .14 by a single wire 21 connecwtepin 22 on the base of the tube.

by using the same circuitnow employed n 'The tube is adapted for use in practically any receiving set of present design using the standard or so-called Navy type of tube.

The pin 22 is preferably so ocated as to correspond in position to the position of the battery pin of the usual tubes. ,1 InFig. 1 I have ilustrated a'simple receivin circuit in which five tubes are emloye to provide two stages of tuned radioa circuit that a bias or 0- battery is sub-- requency amplification, a detector, and two stages of audio frequency amplification. The circuit includes wiresA and A which are the usual A battery wires of a multiple tube receiving circuit. Ordinarily, one

side of the filament of the usual tubes are connected to wire A by wires A The other filament terminal is ordinarily con-,

A battery is not requiredto ener ize lines' A and A to heat therfilamentsfof t etubes,

the grid circuit would, in a standard set, normally be open. According to the present invention, lines A and A are connectedby a small batteiy, frequently referred to in the-art as a battery, and designatedv in the drawings as C, with the negative pole thereof on the line A side of the circuit. This battery closes the otherwise open circuit between A and. A, and at the same time providesa simple, way of putting a strong. negative potential or bias on the gridof,each tube. Sucha bias on the grid is practically essential with tubes of the type havinga unipotential cathode, and the present invention provides a simple manner of ada ting the tube to an apparatus having stanifird circuits and at the same time biasing the grid without openin up the set.

n Fig. 1, the several tubes are designated T, while It is the heater, 0 the cathode, g the grid, and pthe plate oranode.

With the tube as heretofore described, it will be noted that the wires leadin to the heater are at the top ofthe tube, w ile the terminals to the electrodes of the tube are at the bottom. Thispermitsthe heater cir-v cuit H,that is, the alternating current circuit, to be disposed above and away from the receiving circuit. This isclea'rly shown by the wiring diagram of Fig. 1.

As certain capacity effects between the heater and the cathode and the heater circuit and the receiving circuit must necessarily otherwise exist, I have found that by grounding one side of the heater circuit, or connecting it to the cathode circuit throu h wire H, any undesirable effects due to t e use of alternating currents in the heater circuit can be entirely eliminated.

It will thus be seen that I have devised a novel method of and apparatus for adapting alternating current tubes. to present standard types ofsets or circuits, or adaptable to circuits especiallydesigned for my tubes, without any departure from present practice.

I claim as my invention:

1. A three-section radio circuit, including a radio amplifier, a detector, an audio amplifier, an audion tube in each of said sections, cathodes for each of said tubes, heater elements for said cathodes. for heating the same by conduction, a source of alternating current multiply connected to said heater elements, control grids and anodes forveach of said audion tubes, the leads extending from the grids, cathodes andlatesbeing removed from the inductive old of the.

leads extending from, asource .of alternating.

current to the heaters, means connected, be-' tween said grids and said cathodes for-biasing said; cathodes, of the grid cathode circuits,a common con ductor for connectingsaid heaters tosaid means for-tuning certain cathodes, and connections from saidi athodesl extending from said heaters to said cathodes, and means connectedbetween saidcommon circuit and thecommon circuitof said rids for securing at difl'erenceof-potential etween said grids. and said cathodes.

3. The combination with a radio circuit;

for thermionic tubes, of tubes in the circuit having cathodes, looped meansener an alternating currejntfor heating t 1e cathodes, an alternating current circuit multi each of said. audion. tubes, acommon circuitv a ized byply connected with thesaid heating means,

one side of said alternating current circuit being grounded to one side of the radio circuit, a source of-direct-current connected to radlo clrcuit, circuit connections in-- said eluding a conductive path extending from a common conductor connectedto said cathe odes through said source of current to said grids, and means for tuning the circuits of said ids.

4. he combination with a radio circuit for thermionic tubes, of a tube-in the circuit having a cathode and a grid, means energized by alternating current to heat the said cathode, an alternating current circuit, connected with the said heating means, one side of said alternating current circuit being grounded to one side of the radio circuit,

said alternating current circuit for the.

heater being locatedv out of the inductive field of the said radio circuit to separate the alternating current leads from the grid, cathode and plate leads, an inductive-effect vupon the grid, cathode and plate leads from rent leads, a source of unidirectional potential, a circuit including said source ofunidirectional current extending from one side.

of the source of alternating current source.

tuning the to the said grid, and means for circuit of the said grid of sa'idtube.

thereby preventing the alternating cur- 5. The combination with a radio receiving 1 9..

circuit utilizin a plurality of thermionic tubes connecte 'in cascade and each havin an anode, grid and cathode, a heater in eac tube for the cathode adapted to be energized b alternating current to conductively heat tli e cathode to render the same active, a common connection for the grids of the several tubes, acommon connection for the cathodes of the several tubes, a battery in series 'between'the common grid connection and the common cathode connection, a circuit extending-from said common grid connection to one side of the source of alternating current and including said battery, and

means for resonating the grid circuits of said tubes; I

6. A radio receiving circuit including a plurality of radio amplifiers and audio amfilifiers, cathodes for each of said amplifiers,

eater elements for said cathodes for heating the same by conduction, a source of alternating current multiply connected to said heater element, control grids and anodes for said amplifiers, external leads extending from the grid, cathode and plate elements removed rom the inductive field of the leads extending from the source of alternat ing current to the heaters, a source of direct current supply, a common circuit extending I from said ids through said source of current to sai cathodes, means for tuning certain ofsaid grid cathode circuits, a single connectlon outside of said tube extending from said heaters to said cathodes and to ground, and connections from said anodes to said cathodes.

In testimony whereof I hereunto afiix my signature.

FREDERICK S. MoGULLOUGH. 

